Many dispensing systems are known in the art and are used in different industries. These include foam dispensing systems that are used to dispense two component polyurethane foams in various applications. Such foams are made from two reactive foam components that are mixed together to form an expansive foam. This foam has many different uses. It may be used to provide thermal insulation to apparatus, such as whirlpool or spa tubs, or it may be used to provide sound and/or thermal insulation to electronic and mechanical devices, or it can be used to provide packing cushions for the shipping of products. Taking the packing cushion industry dispenser systems, as an example, many foam injection systems utilize a hand-held dispensing gun, or unit, that is connected to remote supplies of the two foam components by a pair of hoses. This hand-held dispensing unit may be fed from a local storage supply of the two foam components by way of a pair of pumps, each of which propel foam components through their respective hoses to the dispenser. Alternatively, the dispenser may be connected to bulk supply sources of these components by lengthy pipes or tubes. Mounted dispensers including automated dispensing systems are also featured where a mounted dispenser feeds into, for example, a conveyed package for a product. A manufacturing facility may utilize multiple foam dispensing stations, each with their own dispenser. Amongst this wide variety of material dispensers there is included dispensers directed at enclosing dispensed material in, for example, a flexible bag. An example is a foam-in-bag dispensing system that forms a bag having foamable material such as polyurethane foam which typically involves mixing certain chemicals together to form a polymeric product while at the same time generating gases such as carbon dioxide and water vapor. If those chemicals are selected so that they harden following the generation of the carbon dioxide and water vapor, they can be used to form “hardened” (e.g., a cushionable quality in a proper fully expanded state) polymer foams. The cushioning quality bag can conform to a product in a package when placed in the package adjacent the product and allowed to expand (or vice versa with the product placed on a yet to fully expand bag) and avoid direct product contact with the product, which can be undesirable, particularly with dispensed material that has an adhesive quality as in polyurethane foam.
Synthetic foams (e.g., polyurethane foam) are typically formed from two mixed components as in liquid organic resins and polyisocyanates placed in a mixing chamber (e.g., a liquid form of isocyanate, which is often referenced in the industry as chemical “A”, and a multi-component liquid blend called polyurethane resin, which is often referenced in the industry as chemical “B”). The mixture can be dispensed into a receptacle, such as a foam-in-place bag (see e.g., U.S. Pat. Nos. 4,674,268, 4,800,708 and 4,854,109), where it reacts to form a polyurethane foam.
The above noted U.S. Pat. No. 4,800,708, which is incorporated herein by reference for background purposes, describes a method and apparatus for successively forming foam filled bags or cushions of the type wherein a foamable composition is deposited in a plastic bag. The formed bags are adapted to be placed in containers with articles being packaged, so that, when the foam expands, the bags and resulting foam conform to the configuration of the articles. The method and apparatus shown in the '708 patent includes advancing a pair of plastic webs through the nip of a pair of drive rollers, while heat sealing the opposing longitudinal side edges of the webs together. Periodically, a predetermined amount of the foamable composition is deposited between the advancing webs immediately above the nip, and the heat sealing along the side edges is periodically and momentarily interrupted to form side edge openings for the subsequent escapement of gases generated during foaming. The advance of the webs is momentarily terminated, and a heated wire then engages the webs to sever the formed bag, while forming a sealed top edge of the formed bag and a sealed bottom edge for the next succeeding bag. The advance then again commences, and the cycle is repeated to successively form the foam filled bags.
Another example of a foam-in-bag dispensing system with a film feed for bag formation and chemical dispensing system is seen in PCT/US2004/014423 filed on 7 May 2004 in the name of IntelliPack of Tulsa Okla., US, and published in English as WO 2004/101252 A2, which PCT application is incorporated herein by reference. In an embodiment of the noted PCT reference, a roll of folded continuous film (known in the art as a “C-fold film material) is drawn by downstream drive rollers so as to pass by an intermediate foam mixing/dispensing module which dispenses foam down into a partially formed bag having a bottom sealed edge formed by sealing jaws positioned below the drive rollers. In the bag making cycle disclosed, the machine (i) seals the lower edge and the open side edge of folded film from the continuous roll; (ii) fills the required length of film with a measured dose of two premixed chemicals that react to produce a urethane foam; (iii) seals the top edge of the bag producing a filled, sealed bag; (iv) and, in a preferred embodiment, cuts the finished, foam-filled bag from the roll to provide for release of a bag as well as sealing of the next bag in advance of the next cycle; and (v) drops the finished bag from the bottom of the bag-making module.
When installed properly, the foam dispenser module is inserted into the open edge of the C-fold web and film webs fold around the dispenser mechanism so that one web of the film passes along the front face of the dispenser module and one along the back; converging further below at the heated sealing jaws. Unfortunately, it is quite common for the film being fed to the nip roller or other driver to halt or jam along its path of travel during the film feed process. In so doing a foam-up condition generally occurs as the dispenser continues dispensing despite the film feed and bag formation hold up, necessitating immediate maintenance or servicing of the foam-in-bag assembly for the removal of the hardened foam which build up in numerous operational areas of the assembly (e.g., a build up that disrupts mechanical movement or electrical connections, etc.). The precision and reliability of the bag making machine and the avoidance of foam dispensing external to a bag or partially formed bag being formed is of greater concern when dealing with a multi-bag production cycle (e.g., a control unit conveying data to a foam-in-bag assembly to make a plurality of cut bags in series). For example, should bag “A” jam, bags “B”, “C”, “D” (or more) may still be scheduled for arrival and receipt of a dosed amount of a dispenser output. Accordingly, even though no bag is sufficiently formed to receive the output of the dispenser, the dispenser continues to output foam for each scheduled bag despite their non-presence, thus aggravating the level of foam spill. Foam, once emitted from the mixing module will quickly spread and solidify within the machine's internal cavities. Foam also tends to drop onto the floor under and around the machine. Such “foam-ups” are problematic and costly to a user. Foam-up occurrences within the dispenser typically results in problems such as those listed below:
a) Significant production downtime for the customer;
b) Time-consuming service calls involving field representatives;
c) Replacement or refurbishment of foam coated internal mechanisms;
d) Hidden, subtle or latent damage to sensitive mechanical components, wiring, or electrical connectors;
e) Permanent cosmetic damage to the painted or plated surfaces and finely machined components of the dispensing system;
f) Foam damage to the operators facility, usually to the floor, or to the products that the operator is attempting to package;
g) Foam damage to the operators clothing and/or shoes;
h) Loss of operator confidence in the foam-in-bag dispensing system.
Unfortunately, it is also quite common, for an operator to run both webs of film together along, for example, the front face of the dispenser module wherein both webs of the C-fold film (or other film type as in double individual layer on single roll film types) are positioned to a common side of the dispenser module. In so doing, the operator also may easily fail to see that both webs are not around the dispenser module properly. This failure is particularly common when both webs are fed to the front of the dispenser, because the view of the rear web is almost completely obstructed by the front web (often a non-transparent film is utilized as in a gray film roll but, even with clear film or translucent film, a misfed film may not be detected). Thus, the operator can misfeed the film without any obvious visual cue that a mistake has been made. Without film webs surrounding both front and back sides of the module, the foam injector nozzle is left open to the machine's internal mechanisms. Foam, once emitted from the mixing module will quickly spread and solidify within the machine's internal cavities. Foam also tends to drop onto the floor under and around the machine. Such “foam-ups” are problematic and costly to a user. With two separate source film feeding as in the above described U.S. Pat. No. 4,800,708, there is typically provided a first film web from a front positioner web source and a second film web from a second film source. Thus, while there is typically a lesser chance for a misfeed, there remains the potential for an undetected film misfeed and a resultant degrading foam-up.
Foam-up occurrences due to this situation of improper film feed lead to similar problems as those listed above for the foam jam situation.
Another foam up problem source is caused by the dispensing system failing to properly position (e.g., losing position control) the device used to allow or preclude dispenser output. For example, undesirable spills have occurred to a dispensing system due to the dispensing system losing control of a chemical flow shut off valving rod position, as in the position of a reciprocating valving rod provided in a mixing module of a chemical flow dispenser. For example, with reference to the crank assembly drive system for the valving rod described in PCT Publication No. WO 2004/101252 A2.                1. System's such as that disclosed in WO 2004/101252 A2 and others such as those that reciprocate a valving rod can be powered up at a time when the valving rod is in the “Open” (or chemical flow out of dispenser outlet) mode position. This allows the dispenser (e.g., the mixing module which retains the valving rod) to dispense the dispenser material (e.g., foam) immediately on system startup with a resultant spillage. Since prior art systems are ill suited for monitoring the system control processor there is not known where the valving rod is in its cycle. While the monitoring system utilized in PCT Publication WO 2004/101252 A2 is an improvement over prior art systems, it is still susceptible to such a problem. That is, unless the reciprocating valve is in it's at home position where the proximity sensor can “see” the piston, the machine cannot respond intelligently at startup, and the system does not generate a signal that foam is coming out of the mixing module at an inopportune time.        2. Also, again relative to the PCT Publication WO 2004/101252, occasionally a proximity sensor fails, and the system cannot find “home” position. When this happens the mixing module can sometimes assume an open position so as to shoot foam when it's not desired.        3. Relative to the PCT Publication WO 2004/101252, occasionally the encoder signal from the motor loses pulses or stops sending pulses altogether which can again create a potential spill situation.        
All of these failure modes as well as potential others of similar nature are difficult to manage because prior art systems are lacking in the ability to know with a great deal of assurance, position of the valving rod unless, for example in the PCT Publication No. WO 2004/101252 example, the rod is at “home” and the proximity sensor is, working properly. Even in that embodiment, the control processor can only infer the position of the valving rod, at all non-home positions, by reliance on counting pulses from the motor encoder.